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Syl Guardian MCP Server

answering

Syl Guardian is answering right now. Last checked 10 min ago. It exposes 2 tools. Last commit 22 Oct 2026.

Causal guardrail: pass/caution/hold verdict on a causal claim before an agent acts.

Uptime history 72 hours of history
72 hours agonow
100.0%
Uptime 24h
91 of 91 checks
2
Tools
read from the server
319 ms
Response time
average over 24h
0
Stars
last commit 22 Oct 2026

What changed 2

Every tool that appeared, vanished or quietly changed what it asks for. Recorded since 23 October 2026. No other catalogue keeps this.

23 Oct 2 tools changed the parameters they ask for guardian_request_upload, guardian_review

Nothing serious here today

Today is the operative word: we check Syl Guardian every 15 minutes and re-read its code on every release. Watch it and you find out the day that stops being true.

Three servers free · no card

Connect this server

Endpoint below is the one we actually reach during checks — not the one copied from a README. Last verified 10 min ago.

run in your terminal
claude mcp add guardian --transport http https://guardian.sylai.io/mcp
Settings → Connectors → Add custom connector, then paste this address
https://guardian.sylai.io/mcp
~/.codex/config.toml
[mcp_servers.guardian]
url = "https://guardian.sylai.io/mcp"
.cursor/mcp.json
{
  "mcpServers": {
    "guardian": {
      "url": "https://guardian.sylai.io/mcp"
    }
  }
}
.vscode/mcp.json
{
  "servers": {
    "guardian": {
      "type": "http",
      "url": "https://guardian.sylai.io/mcp"
    }
  }
}

Available tools 2

Read directly from the server with tools/list, grouped by what they act on. If a tool disappears, we record the date.

guardian
guardian_request_upload
Get a pre-signed URL for uploading a large CSV (more than ~200 rows). Use this instead of pasting rows into ``guardian_review``. Returns ``upload_url``, ``dataset_id`` and a ready-to-run ``curl`` command: run it (replace ``data.csv`` with your file; gzip is accepted with ``Content-Encoding: gzip``), then call ``guardian_review`` with ``dataset_id`` (and no ``csv``/``data``). The URL is single-use and expires after 30 minutes; the dataset is only usable by the same API key, and is single-use too: it is deleted when ``guardian_review`` reads it (even if that review fails), so request a new upload to retry. This call does not consume review quota.
guardian_review
Sanity-check a causal claim ("cause drove effect") before acting on it. Provide exactly one of ``csv`` (CSV text), ``data`` (list of row objects) or ``dataset_id`` (a dataset uploaded via ``guardian_request_upload``; use this for more than ~200 rows; single-use, deleted when reviewed) containing columns named by ``cause`` and ``effect``. Returns a verdict -- ``pass`` (act), ``caution`` (act carefully), or ``hold`` (do not act; the effect looks confounded or unsupported) -- with the naive correlational effect versus the confounder-adjusted causal effect and its confidence interval, the confounders adjusted for, a confidence score, a plain-English interpretation, and a recommended action. All numbers are deterministic statistics (never LLM-generated); only the interpretation prose may be AI-written. Args: cause: Treatment column the claim says drives the outcome (e.g. "ad_spend"). effect: Outcome column (e.g. "new_customers"). csv: Dataset as CSV text (header row required). data: Dataset as a list of row records (alternative to ``csv``). dataset_id: ID returned by ``guardian_request_upload`` after uploading the CSV (alternative to ``csv``/``data``; for datasets above ~200 rows). Single-use: the dataset is deleted when reviewed, so re-upload to retry. known_confounders: Columns to adjust for; otherwise discovered automatically. context: Free-text business context, e.g. "Q3 promo evaluation". units: Display-only unit hints by column, e.g. {"ad_spend": "USD"}. step: A concrete treatment step (e.g. 1000 for a $1,000 spend increase) to restate the effect in business terms (cost per incremental outcome, ...). time_col: Column to order rows by for time series (autocorrelation-robust standard errors and adstock). adstock: Opt-in geometric-adstock transform for a lagged/carryover treatment. se: Standard-error flavor; "auto" diagnoses autocorrelation when ``time_col`` is given. test_design: ``true`` (or an options object) also returns how many periods a spend-cut test needs to confirm the effect.

Endpoints

URLTransportStateLatencyChecked
https://guardian.sylai.io/mcp streamable-http answering 208 ms 10 min ago

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Syl Guardian — questions

Answers built from our own checks of this server.

What can Syl Guardian do?
It exposes 2 tools, read directly from the server on our last check. Among them: guardian_request_upload, guardian_review. The full list with descriptions is on this page — we take it from the server itself via tools/list, not from a README. How MCP servers expose tools in the first place →
Is Syl Guardian working right now?
We send a real MCP handshake every 15 minutes. Over the last 24 hours 91 of 91 checks got a reply (100.0%), average response time 319 ms. The bar chart above shows every period we have measured.
How do I connect Syl Guardian?
Copy the ready config from this page. We generate it for Claude Code, Claude Desktop, Codex, Cursor and VS Code, each in the form that client actually reads. It is a remote server, so there is nothing to install — the client connects to the address.
Does Syl Guardian need an API key?
No. Syl Guardian completed a full MCP handshake with us as an anonymous client and listed its tools without asking for anything. All 2 of them are readable on this page. This is what we observed, not what the docs claim.
How fast is Syl Guardian?
It answers our handshake in 319 ms on average, which is faster than 51% of all working MCP servers we measure. The comparison comes from our own checks across the whole registry, every 15 minutes.
Is Syl Guardian open source?
The code is open source: it is published under the MIT licence, 0 stars on GitHub and 1 open issue. The licence covers the code in the repository, not the hosted service at guardian.sylai.io, which runs on its operator's own terms.